The present invention is related to phase detection of a signal. The determination of phase of a signal and determination of phase shift of a signal are basic processes having numerous applications. Examples include communications, FM discriminators, heterodyne interferometry, astronomy, and scientific research.
A specific application for which the present invention may be used is heterodyne interferometry. Heterodyne interferometry can be used for nondestructive evaluation (NDE) of materials. Heterodyne interferometry has been used for vibration measurement of the thermal protection tiles on the space shuttle orbiter. As used for such measurements, this technique has been conducted under specially controlled laboratory conditions. Heterodyne interferometry or other NDE techniques (optical, vibrational or sonic) could be developed for the inspection of completed parts and the sensing of manufacturing processes for feedback control of those processes. However, such techniques, as currently employed, require delicate alignment and calibration which make them impractical outside of the laboratory. It would make such techniques usable for a wide variety of industrial applications if a means were provided that made such techniques less delicate and more reliable under normal manufacturing conditions. It is for such an objective that the present invention provides an economical and reliable means for phase determination measurements.
Accordingly, it is an object of this invention to provide a means for phase detection of a signal.
It is a further object of this invention to provide a means for phase detection that can be implemented economically.
It is another object of this invention to provide a method and apparatus for phase detection that can make certain processes like heterodyne interferometry inspection adaptable to a wide variety of usages.
It is yet another object of this invention to provide a means for phase detection that can be applied to a various applications such as communications, FM discriminators, heterodyne interferometry, astronomy, and scientific research.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.